The Different Drug Abuse Testing Methods
We all know that there are different kinds of drug tests and each one of them is used for the same objective - to detect drug users. Depending on the type of drug test, a biological specimen (urine, blood, saliva, sweat, or hair) is technically analyzed to detect the presence of drugs or their metabolites.
The methods by which the different types of drug tests are, in turn, tested are quite similar in many ways. The specimen is placed in an appropriate container, sealed, and then sent to a laboratory for analysis. At the laboratory, the specimen's seal is first checked before being accepted for testing; that is, the seal should not show any signs of tampering. If it does, the laboratory will reject the specimen and will not test it.
All drug tests are initiated with one particular step: make the specimen testable. For some of the drug tests, urine or saliva can be used in its unaltered, presently existing condition. For other tests, however, there is a need to extract the drugs from the specimens in advance.
Other specimens require some preparation prior to testing:
* Plasma from the blood specimen may have to be separated with the use of centrifuge, a machine that makes use of centrifugal force to separate substances of different densities.
* Sweat sample from patches used in sweat drug screen is immersed in a solvent to break up any drugs present.
* Hair sample is first washed before breaking down the keratin with enzymes.
Drug testing conducted in laboratories is performed in two levels with the use of two different types of testing methods: screening test and confirmation test.
Screening test method:
This method is used for all samples that are sent to the laboratory. Screening tests are usually performed by immunoassay, a biochemical test that measures the concentration of a substance in a biological fluid, such as urine or serum. The two most common immunoassays are the enzyme multiplied immunoassay technique (EMIT) and the enzyme-linked immunosorbent assay (ELISA). In measuring the concentration of a substance in the fluid, these tests make use of the antibody's reaction to its antigen.
Samples that come out negative are discarded and reported as such. Those that turn out positive are sent to the next level for further testing (the confirmation test method).
Confirmation test method:
This method is used only to specimens that test positive during the screening test. The test is done using mass spectrometry (MS), a technical method for the determination of the basic constituents of a sample or molecule. While this method turns out precise results, it is very costly to use.
A false-positive result from the screening test will be negative on the confirmation test. On the other hand, a positive result from both tests will be reported as such.